Many electronic components include dies, also known as integrated circuit chips, attached to next level packages such as a substrates, interposers, printed circuit boards, etc. A may be attached to a next level package using a flip chip or controlled collapse chip connection C4 technique. In the C4 technique, the die is typically bonded to the next level package with bumps or interconnects formed of solder and aluminum, copper, or other conductive materials. In this technique, the die, interconnects and next level package are heated to form a bond, a process commonly known as reflowing. Heating is typically done by heating the die, next level package, and interconnects simultaneously in a reflow oven at elevated temperatures.
While this approach is effective for bonding the die to the next level package, it can result in mechanical stresses in an assembly so produced due to differing coefficients of thermal expansion between the die and the next level package materials. If the die and the next level package have different coefficients of thermal expansion, they will not expand or contract to the same extent when heated or cooled through the same temperature range in the reflow oven. After bonding, removal from the reflow oven, and cooling, the resulting assembly can thus suffer from residual mechanical stresses which are greater than desired. These stresses can lead to defects in the assembly such as cracks in interlayer dielectric (ILD) layers.